PARIS -- Once Paris Saint-Germain complete the formalities of turning Kylian Mbappe's season-long loan from Monaco into a permanent deal worth €180 million this summer, the French club will have spent just over €1 billion on players since the arrival of their Qatari owners in June 2011.

For that huge investment, Qatar Sports Investments have been rewarded with four Ligue 1 titles, three Coupes des France and four Coupes des Ligues, yet nothing more than broken dreams in Europe. Beyond the French league, PSG have become the great underachievers of the Champions League and have still to reach their first semifinal.

They will have to wait at least another year for that to happen following the 5-2 aggregate defeat against reigning champions Real Madrid, with Zinedine Zidane's team rubbing salt deeper into Parisian wounds by ending PSG's two-year unbeaten home record with a 2-1 victory at Parc des Princes on Tuesday.

Having broken the world transfer record last summer -- they actually obliterated it -- by spending £198 million to lure Neymar from Barcelona, this was supposed to be the year that PSG made the breakthrough in the Champions League. They had prised Neymar from the Camp Nou, landing a blow on Barcelona's pride, and also beat Real and Manchester City to the signing of Mbappe.

But for all of their lavish spending and statements of financial power, are PSG any closer to becoming a platinum member of Europe's elite? They have the money, the ambition and the grand stage of Paris, but as they slid out of the Champions League, PSG looked more like a disjointed group of second-tier stars than a team on the brink of winning the greatest club prize of all.

City, whose revolution under Abu Dhabi's Sheikh Mansour bin Zayed al Nahyan is approaching its 10th anniversary this September, have also spent just over €1 billion on players since being bought out by supremely wealthy owners.

They had a three-year head start on PSG, but the French club's ability to dominate a less competitive domestic league enabled them to catch up and move ahead of City, becoming an established Champions League outfit while the English club struggled initially to even progress from the group stages. But when you compare the two clubs now, it is clear that one (City) has benefited from a strategic, long-term approach, while the other (PSG) is, for want of a better phrase, throwing money at the problem and hoping that it works.

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The performance of Unai Emery's players against Real was not that of a team working to a philosophy of their coach or club. When you watch City under Pep Guardiola, there is a clear style of play, a sense of every player being bought for a reason, to play a certain way in a certain system. After just 18 months under Guardiola, City now have an identifiable DNA of adventurous, slick, attacking football. If PSG have their own DNA, it is obscured by dollar signs and euros.

Their recruitment strategy does not appear to be based on buying building blocks to make a successful team. Rather, it is about headline-making signings. It was Zlatan Ibrahimovic, Edinson Cavani and Angel Di Maria before Neymar and Mbappe joined the party last summer.

Other than Thiago Silva, the majestic Brazilian defender signed from AC Milan in 2012, there have been precious few world-class defenders added to the squad. If anything, PSG have adopted the Manchester United approach to building a squad rather than that of City: stars first, bricks and mortar second.

Despite the similarities in spending between PSG and City in the transfer market, it is worth noting that City's record signing is the €65 million (£57.1 million) outlay on defender Aymeric Laporte in January. PSG, United, Real, Barcelona and Juventus all have bigger record signings than City, who tend to make expensive signings throughout their team rather than bet the ranch on one player for an eye-watering figure.

But when the dust settles in PSG's latest Champions League blowout, perhaps the club's owners will look at the City model and decide to alter their approach. City hired Guardiola to give them style and success within a long-term vision, but "long term" does not exist in the PSG phrasebook. If "long term" was a dazzling, young striker, however, they would probably break the bank to sign him.

Yet if PSG want to crack the Champions League, they need to take a new approach. They must plan for the long term, invest in every area of their team and allow a coach to build from the bottom up.

Because if €1 billion cannot deliver the ultimate success, it would suggest that money alone is not the answer.